Friday, June 8, 2007
Updated: May 5, 2:44 PM ET
What are the ESPN Player Ratings?
By Jeff Bennett
A few years ago I was challenged to devise a formula with the goal of ranking players. Obviously, there are countless systems already in place in the baseball community. I did not attempt to create a new statistic or metric. Instead, I took the approach of using traditional statistics (with some variations) and using the daily volatility of where each player ranked in the major leagues to create a rating system. Each player's performance is put into direct context with his peers.
The real challenge was to find the statistics and values necessary to integrate all of the different types of players (batters, starting pitchers, relievers) into one rating system. For instance, what percentage of a batter's overall rating is his major league rank in batting bases accumulated (TB + BB + HBP) or his rank in net steals? ERA is obviously a very good indicator of a starting pitcher's performance, but what other statistics tell part of the story? How heavily should I weigh a relief pitcher's ability to limit inherited runners? Trevor Hoffman is likely going to the Hall of Fame, but he rarely comes into a game with runners on base.
I did not use specific results from previous studies on how each statistic correlated to team wins or runs scored. However, the results of these rankings do seem to have a high correlation with the postseason awards, albeit with some notable exceptions (see below for examples).
The Player Rater allows users to rank players in various ways -- the top 100 players in the majors, the top candidates for MVP and Cy Young, the five NL shortstops, the top five AL starting pitchers, the top 10 Brewers, and so on. One of the most interesting tools is using the ratings to populate each league's 32-man All-Star roster. So have fun, don't take them too seriously, but then again, don't be surprised when MLB awards are announced in November. Since 2005, the batters rated highest for their league have been named MVP five of eight times and finished second in the voting the other three times. The top-rated starting pitchers have won six of the eight Cy Young Awards and finished second and third the remaining two times.
How players are rated
The ESPN Player Ratings give a rating ranging from 0 to 100 to all players based on points players accumulate off their current standings in the major leagues in numerous statistical categories and metrics. Consideration, although relatively minimal, is given for the difficulty of a player's defensive position and how often position players participate in a win.
The different categories are weighted individually, and there is a mix of counting stats and average stats. Playing time and innings pitched are important factors. A perfect rating is a score of 100, which would only be attainable by a catcher
who led the major leagues in bases accumulated, runs produced, OBP, BA, HR, RBIs, runs, hits and net steals, and his team having a winning percentage of at least .615 when he plays.
Not every player earns a score. Batters who have not appeared in at least half of their team's games or pitchers who do not excel in any of the designated measurements will not be rated. Typically, 475-500 players earn points to qualify for the ratings.
Players receive points for their major league rankings in the following disciplines:
• Batters: Batting bases accumulated, runs produced, OBP, BA, HRs, hits, runs, RBIs, net steals, difficulty of defensive position, and team win percentage based on the games in which they play, not the overall team win percentage.
• Starting pitchers: ERA compared with league average weighted by IP, wins weighted by win percentage, defensive independent bases allowed per IP (limiting HR, BB and HBP), strikeouts, opponents' BA, and innings pitched.
• Relievers: Wins and saves with a stiff penalty for blown saves, ERA compared with league average weighted by IP, K-BB ratio, opponents' BA, and preventing inherited runners from scoring.
Following are some definitions of terms listed above:
• Batting bases accumulated = TB + BB + HBP
• Runs produced = Runs + RBI - HR
• Team win percentage = points awarded for following ranges
Note: Players are eligible only if they played in 50 percent of team games.
• Difficulty of position = maximum points awarded for C and zero for DH
Note: Players are eligible only if they played in 50 percent of team games. Position defined as the position played in the majority of games. If there is a tie, the position with the highest point value is awarded. Players are eligible only if plate appearances are greater than or equal to 2.5 * team games.
Here's the order:
C: 50 points
SS: 35 points
2B: 30 points
3B: 25 points
CF: 20 points
RF: 15 points
LF: 10 points
1B: 5 points
DH: 0 points
• ERA vs. league average weighted by IP = [(League ERA - ERA) / league ERA] * IP
• Wins weighted by win percentage = wins * win percentage
• Defensive independent bases allowed per IP = [( HR allowed * 4) + BB + HBP] / IP]
• Saves and wins with blown save penalty = (saves * 2) + wins - (blown saves * 3)
A look at past season's results
Jeff Bennett is the senior director of research for ESPN.